We plan to provide a first order sequence to reactivity algorithm that will allow for prediction of the equilibrium constants for association of protein inhibitors of serine proteinases with their cognate enzymes. Such an algorithm, if successful, would be a tremendous intellectual advance in understanding of the energetics and specificity of protein-protein interactions. However, its most immediate advantage would be the ability to design highly specific inhibitors for physiologically and medically important serine proteinases. Such designs will be made. Inhibitors of this type may be of value in prevention of emphysema, excessive blood clotting, excessive clot dissolution, Alzheimer's disease, etc. There is a large pharmaceutical interest in such inhibitors.